US10125352B2 - Method for producing enveloped viruses - Google Patents

Method for producing enveloped viruses Download PDF

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US10125352B2
US10125352B2 US15/022,049 US201415022049A US10125352B2 US 10125352 B2 US10125352 B2 US 10125352B2 US 201415022049 A US201415022049 A US 201415022049A US 10125352 B2 US10125352 B2 US 10125352B2
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    • C12N2760/20222—New viral proteins or individual genes, new structural or functional aspects of known viral proteins or genes

Definitions

  • the invention relates to a process for producing enveloped viruses produced by a cell culture in a mildly acid medium.
  • the processes of the invention are useful for producing these particles for applications in biomedical or biotechnological research in order to facilitate the production yields notably when it is carried out on a large scale and under conditions observing good manufacturing practice (GMP).
  • Enveloped viral vectors and notably lentiviral vectors such as those derived from the human immunodeficiency virus-1 (HIV-1) are promising tools within the scope of gene therapy approaches.
  • mass production of clinical grades of such vectors remains a challenge at the present time.
  • Several approaches have been proposed for improving their production: optimization of the transfection of the plasmids required for producing the vector in the host cells (e.g., optimization of the transfection agent, of the cell density, of the ratio of plasmids, etc.) or cell culture conditions focused on particular cell metabolism routes (e.g., addition of lipids, cholesterol, chloroquine, sodium butyrate, etc.) (Ansorge et al. 2010; Schweizer and Merten 2010).
  • the inventors have the idea of extending this field and of optimizing physico-chemical parameters, and were more particularly interested in the pH conditions.
  • the neutrality of the pH of the medium is considered as a critical parameter for cultivating mammal cells.
  • a study reported that pseudotyped lentiviruses with envelope glycoproteins of the virus of vesicular stomatitis (VSV-G) are unstable at pH 6 in a phosphate buffer (Higashikawa and Chang 2001). Considering these elements, the person skilled in the art would have considered that the reduction of pH in culture media would have a negative impact on the production of enveloped viruses.
  • the present invention results from the observation of improvement in the production of enveloped viruses when the cells producing said viruses are cultivated in a mildly acid medium.
  • said mildly acid conditions gave the possibility of producing viruses having infectious titers two to three times greater than those obtained in a conventionally used neutral medium.
  • the object of the invention is the use of mildly acid conditions for producing an enveloped virus. More particularly, the invention relates to a process for producing an enveloped lentiviral vector, characterized in that the culture medium used for cultivating the host cells producing said vector is a mildly acid medium.
  • the invention therefore relates to a process for producing enveloped vectors characterized in that said vectors are produced under mildly acid conditions.
  • the expression “mildly acid condition” refers to the pH of an aqueous solution comprised between 5 and 6.6, in particular between 5.5 and 6.6 or between 5 and 6.2, more particularly between 5.8 and 6.2.
  • the pH will notably be equal to 5.5, 5.6, 5.7, 5.8, 5.9, 6, 6.1 or 6.2. According to a particular embodiment, the pH is of about 6.
  • the selected pH will also depend on the buffering power of the medium used, which the person skilled in the art will be able to easily determine considering his/her general knowledge.
  • a solution notably the pH of a cell culture medium. He/she may notably introduce into said solution a solution of an acid, notably of a strong acid such as hydrochloric acid. If need be, a solution of a base, notably of a strong base such as sodium hydroxide, may be used for readjusting the pH to bring it up to the desired value.
  • a solution of a base notably of a strong base such as sodium hydroxide
  • the process used for producing enveloped viruses applies processes and materials well known in the field.
  • the person skilled in the art may refer to his/her general knowledge in the production of enveloped viruses, notably illustrated by Ansorge et al. 2010; Schweizer and Merten 2010; and Rodrigues et al. 2011.
  • virus designates both a natural virus, as found in nature, and a modified virus, for which the genome includes modifications relative to that of the parent virus from which it is derived. This may be an attenuated virus, which has lost all or part of its pathogenic power as compared with the natural virus from which it is derived. Its genome is modified in vivo during successive passages in a cell culture or in a living organism.
  • virus may also refer to a recombinant virus, for which the genome is modified in vitro by genetic engineering techniques.
  • the modification may, for example, allow inactivation of at least one essential gene for viral replication (making the virus deficient for replication) and/or insertion of a DNA fragment coding for a protein or a heterologous RNA (normally not coded by the natural virus). In the latter case, this is referred to as a “viral vector”.
  • the insertion takes place in a suitable region of the viral genome, so as to allow expression of the heterologous DNA fragment in a target cell.
  • the term “virus” also refers to pseudo-viral particles, i.e., viral particles either without any envelope glycoprotein at their surface, or without a genome and obtained by spontaneous assembling of structural and/or enzymatic proteins of the virus.
  • the enveloped virus is a viral vector.
  • the viral vector is notably derived from a retrovirus, for example a lentivirus.
  • the retroviral vectors produced according to the invention are notably derived from alpha-retroviruses (such as ALV for avian leukosis virus), from beta-retroviruses (such as MMTV for mouse mammary tumour virus), from gamma-retroviruses (such as the different types of MLVs for murine leukemia virus), from delta-retroviruses (such as the different types of HTLV for human T-lymphotropic virus), from epsilon-retroviruses (such as WDSV for Walleye dermal sarcoma virus), from spumaviruses (such as HFV for human foamy virus and SFV for simian foamy virus), from primate lentiviruses such as the different types of human immunodeficiency viruses (HIV for human immunodeficiency virus), the
  • the retroviral vector in particular lentiviral vector is pseudotyped, i.e. it comprises an envelope glycoprotein derived from a virus different from the virus from which is derived the retroviral particle, a modified envelope glycoprotein or a chimeric envelope glycoprotein.
  • the retroviral vector is pseudotyped with an envelope glycoprotein derived from the virus of vesicular stomatitis (VSV-G) or from the gibbon leukemia virus (GALV for gibbon ape leukaemia virus), although the person skilled in the art may contemplate the use of other viral envelope glycoproteins (Frecha et al. 2008).
  • the retroviral vector is pseudotyped with a modified envelope glycoprotein such as GALVTR (an envelope glycoprotein of GALV for which the intravirion C-terminal end has been replaced with the C-terminal end of the envelope glycoprotein of the amphotropic human leukaemogenic virus A-MLV, thus allowing highly efficient incorporation of the envelope glycoprotein into the lentiviral particle) (Christodoulopoulos and Cannon 2001).
  • GALVTR an envelope glycoprotein of GALV for which the intravirion C-terminal end has been replaced with the C-terminal end of the envelope glycoprotein of the amphotropic human leukaemogenic virus A-MLV
  • the retroviral vector is pseudotyped with a chimeric envelope glycoprotein such as the envelope glycoprotein of the measles virus in which a fusion protein coding for the variable region of heavy and light chains of an immunoglobulin (scFv for single chain variable fragment) or a protein with repeated ankyrin domains (DARPins for designed ankyrin repeat proteins) have been inserted in order to allow specific targeting of a given receptor at the surface of the target cells (Anliker et al. 2010; Munch et al. 2011).
  • a chimeric envelope glycoprotein such as the envelope glycoprotein of the measles virus in which a fusion protein coding for the variable region of heavy and light chains of an immunoglobulin (scFv for single chain variable fragment) or a protein with repeated ankyrin domains (DARPins for designed ankyrin repeat proteins) have been inserted in order to allow specific targeting of a given receptor at the surface of the target cells (Anliker et al. 2010; Mun
  • the viral envelope glycoprotein used for pseudotyping the retroviral vector is derived from an envelope glycoprotein of a virus belonging to the family of rhabdoviridae, notably of the Vesiculovirus genus (e.g., VSV-G) or of the Lyssavirus genus (e.g., rabies virus, Mokola virus); to the family of Arenaviridae (e.g., lymphocyte choriomeningitis virus (LCMV)); to the family of togaviridae, more particularly of the alphavirus genus (e.g., Ross River Virus (RRV), Sindbis virus, Semliki Forest Virus (SFV), Venezuelan equine encephalitis virus, Western equine encephalitis virus); to the family of filoviridae, most particularly of the filovirus genus (e.g., Ebola virus, Lassa virus); to the family of retrovirida
  • VSV-G Vesiculovirus genus
  • the envelope glycoprotein used for pseudotyping is more particularly a modified envelope glycoprotein, for example an envelope protein fused with an antibody fragment with a single variable chain ScFV, such as measles-ScFV, Tupaia-ScFV, Sindbis-ScFV envelope glycoprotein; an envelope protein fused with Ankirine repeat domains such as a measles/DARPins envelope protein; or further a VSV-G+nanobody display with defective binding protein.
  • a modified envelope glycoprotein for example an envelope protein fused with an antibody fragment with a single variable chain ScFV, such as measles-ScFV, Tupaia-ScFV, Sindbis-ScFV envelope glycoprotein; an envelope protein fused with Ankirine repeat domains such as a measles/DARPins envelope protein; or further a VSV-G+nanobody display with defective binding protein.
  • the retrovirus more particularly the lentivirus, produced according to the invention is pseudotyped with a VSV-G, measles, GALV or BAEV (if the virus is a retrovirus), GALVTR or BAEVTR (if the virus is a lentivirus) or baculovirus gp64 glycoprotein.
  • the enveloped virus may moreover contain a transgene of interest introduced into its genome.
  • the transgene of interest will depend on the specific use for which the enveloped viral vector is intended.
  • a transgene of interest coding for a therapeutic RNA e.g., a transgene of interest coding for a complementary antisense RNA of a target RNA or DNA sequence
  • a gene therapy transgene coding for a deficient or absent protein in a subject affected with a pathology e.g., a transgene used for vaccination with DNA, i.e. a transgene coding for a protein, the expression of which will induce vaccination of the receiving organism against said protein.
  • the process according to the invention therefore allows production of an enveloped viral vector which may be used in gene therapy.
  • the process according to the invention is advantageously compatible with good laboratory practice and gives the possibility of contemplating large scale production of enveloped viral vectors, notably of lentiviral vectors, in particular pseudotyped lentiviral vectors (in particular with the VSV-G or GALVTR envelope proteins).
  • the four following elements are introduced into the host cell: an expression cassette comprising a lentiviral gagpol gene, an expression cassette comprising a lentiviral rev gene, an expression cassette of a transgene of interest comprised between a lentiviral LTR-5′ and LTR-3′, and an expression cassette of envelope glycoprotein(s).
  • the enveloped virus notably a retroviral vector, more particularly a lentiviral vector
  • a retroviral vector is produced from a stable line expressing one or several elements required for producing an enveloped virus (Miller 2001; Rodrigues et al. 2011), such as the human productive line GPRG-EF1 ⁇ -h ⁇ c OPT which constitutively produces a lentiviral vector derived from HIV-1 pseudotyped with the VSV-G envelope glycoprotein (Greene et al. 2012), or for example the murine producing line PG13-MFG-GFP which constitutively produces the gamma-retroviral vector MLV pseudotyped with the GALV envelope glycoprotein (Merten 2004).
  • the human productive line GPRG-EF1 ⁇ -h ⁇ c OPT which constitutively produces a lentiviral vector derived from HIV-1 pseudotyped with the VSV-G envelope glycoprotein
  • the murine producing line PG13-MFG-GFP which constitutively produces the gamma-retro
  • the enveloped virus is produced from a mammal host cell transiently transfected with one or several plasmids coding for the elements required for producing the virus.
  • said elements are introduced into the cell by means of 4 plasmids: a plasmid bearing an expression cassette comprising a lentiviral gagpol gene, a plasmid bearing an expression cassette comprising a lentiviral rev gene, a transfer plasmid comprising an expression cassette of a transgene of interest comprised between a lentiviral LTR-5′ and LTR-3′ and a plasmid bearing an expression cassette of envelope glycoprotein(s).
  • the cultivation in a mildly acid medium is carried out according to the invention as soon as the production of the virus is started, i.e., the producing cell is cultivated in a medium of which the pH is mildly acid before contact with the producing cells.
  • the cell is cultivated in a mildly acid medium 5 to 24 hours after transfection, more particularly 10 to 20 hours post-transfection, even more particularly 16 to 20 hours post-transfection.
  • the host cell may be selected from any cell allowing production of an enveloped virus.
  • said cell is selected from a human cell (HEK293, HEK293T, HEK293FT, Te671, HT1080, CEM), a muridae cell (NIH-3T3), a mustelid cell (Mpf), a canid cell (D17) (Miller 2001; Miller and Chen 1996; Merten 2004; Rodrigues et al. 2011; Stacey and Merten, 2011).
  • the cells are cultivated in a suitable medium for cultivating mammal cells and for producing an enveloped virus.
  • the medium may moreover be supplemented with additives well known in the field such as antibiotics, serum (notably fetal calf serum, etc.) added in suitable concentrations.
  • the medium used may notably comprise serum or be without any serum.
  • the media for cultivating mammal cells are well known in the field.
  • DMEM Dulbecco's Modified Eagle's medium
  • RPMI1640 or a mixture of different culture media, for example DMEM/F12, or a medium without any serum like optiMEM®, optiPRO®, optiPRO-SFM®, CD293®, Freestyle F17® (Life Technologies) or Ex-Cell® 293 (Sigma-Aldrich).
  • any agent allowing transfection of plasmids may be used.
  • the use of calcium phosphate or polyethylenimine may notably be made, although other agents may be contemplated by the person skilled in the art (Ansorge et al. 2010).
  • the conditions (notably amount of plasmid(s), ratio between the plasmids, ratio between the plasmid(s) and the transfection agent, the type of medium, etc.) and the transfection period may be adapted by the person skilled in the art according to the characteristics of the produced virus and/or of the transgene introduced into the transfer plasmid.
  • the enveloped virus is then harvested from the culture supernatant according to methods well known in the field.
  • the process according to the invention comprises the following steps:
  • the produced enveloped virus is a lentivirus produced after transfection of the cells by means of four plasmids: one plasmid bearing an expression cassette comprising a lentiviral gagpol gene, one plasmid bearing an expression cassette comprising a lentiviral rev gene, one transfer plasmid comprising an expression cassette of a transgene of interest comprised between a lentiviral LTR-5′ and LTR-3′ and one plasmid bearing an expression cassette of envelope glycoprotein(s).
  • the envelope protein is derived from the VSV virus (in particular VSV-G envelope) or from the GALV virus (in particular the GALVTR modified glycoprotein for lentiviral vectors).
  • viruses or viral vectors produced may then be purified according to processes well known to the person skilled in the art (Segura et al. 2011).
  • the invention moreover relates to a medium for cultivating mammal cells, said medium being mildly acid.
  • the culture medium is at a pH comprised between 5.5 and 6.6, more particularly between 5.8 and 6.2. More particularly, the pH of the culture medium according to the present invention is of about 6.
  • the culture medium is mildly acid DMEM, notably with a pH as defined hereinbefore.
  • the culture medium according to the invention is a DMEM medium with a pH comprised between 5.8 and 6.2, in particular a DMEM medium of pH 6. It is understood that the culture medium according to the invention is characterized by a mildly acid pH before cultivating the cells.
  • the invention moreover relates to a kit for applying the process for producing enveloped viruses as defined above, comprising a mildly acid culture medium, or a culture medium accompanied by one or several useful solutions for bring the pH of said medium to a mildly acid value, the kit further comprising:
  • the kit of the invention is intended for producing an enveloped virus according to the invention.
  • it may further comprise instructions for use of the different constituents of the kit allowing production of an enveloped virus according to the invention.
  • these instructions may indicate how the cells intended for the production have to be transfected with the suitable plasmids and cultivated in the culture medium.
  • the instructions indicate that the cells producing the enveloped virus have to be cultivated in a culture medium with a mildly acid pH as detailed above.
  • the invention also relates to a kit for applying the process for producing enveloped viruses as defined above, comprising (i) means for applying said process and (ii) instructions to be followed for applying the process.
  • the means comprised in the kit are selected from among one or several of the following means:
  • a kit according to the invention may thus notably comprise the means (a) and (b), (a) and (c), (b) and (c) or (a) and (b) and (c).
  • the invention also relates to a kit for applying the process for producing enveloped viruses as detailed above, comprising a culture medium accompanied by one or several useful solutions for bringing the pH of said medium to a mildly acid value.
  • FIG. 1 Production of a lentiviral vector (LV) pseudotyped with the GALVTR envelope (GALVTR-LV) under diverse pH conditions.
  • the culture media (DMEM/FCS) were buffered to the indicated pH with hydrochloric acid or sodium hydroxide.
  • the pH indicator contained in the medium (phenol red) has a color ranging from yellow (pH 6) to violet (pH 8).
  • GALVTR-LV particles were produced from HEK293T cells cultivated in a DMEM/SVF medium at the indicated pH value.
  • the infectious titers (TU/ml) were determined after transduction of HCT116 cells and quantification of the expression level of the GFP transgene by flow cytometry.
  • the contents of the supernatants of physical particles GALVTR-LV were quantified by quantitative measurement of the capsid p24 of HIV-1 by means of a commercial ELISA kit.
  • the specific activity corresponding to the ratio between the infectious titers and the amount of physical particles (TU/ng of p24) is illustrated under the histograms. The results represent the average of two independent experiments ⁇ the standard deviation. Seven batches of GALVTR-LV vector were produced in the medium at pH 7.2 or pH 6 and were titrated for their contents of infectious particles (c) or of physical particles (d). (e) The specific activity of each GALVTR-LV supernatant is illustrated. The bars indicate the average value of the distributions.
  • FIG. 2 Production of a VSV-G-LV lentiviral vector under neutral or slightly acid pH conditions.
  • Six VSV-G-LV vector batches were produced from HEK293T cells cultivated in DMEM/SVF medium at the indicated pH. The infectious titers were determined as in FIG. 1 b .
  • the amount of physical particles was determined by quantitative measurement of the p24 capsid of the HIV-1 by means of a commercial ELISA kit.
  • the specific activity of each VSV-G-LV supernatant is illustrated. The bars indicate the average value of the distributions.
  • FIG. 3 Production of a GALV-MLV gamma-retroviral vector under neutral or slightly acid pH conditions.
  • Six GALV-MLV vector batches were produced from HEK293T cells cultivated in DMEM/SVF medium at the indicated pH.
  • the infectious titers were determined as in FIG. 1 b .
  • the bars indicate the average value of the distributions.
  • FIG. 4 Study of the stability of GALVTR-LV lentiviral particles after several freezing/thawing cycles.
  • FIG. 5 Study of the stability of GALVTR-LV lentiviral particles after exposure to a temperature of 37° C.
  • the infectious titers were determined as in FIG. 1 b .
  • the data are represented either as the infectious titers obtained from three independent experiments or (b) the average of the infectious titers ⁇ the standard deviation and normalized to 100% relative to the control condition (a condition corresponding to a GALVTR-LV vector not exposed at 37° C.).
  • FIG. 6 Study of the expression levels of intracellular p55gag in producing HEK293T cells cultivated in a medium at neutral or slightly acid pH.
  • HCT116 cells derived from a human colorectal carcinoma (CCL-247; ATCC, Manassas, Va.), HEK293T cells of a human embryo kidney (Merten et al. 2011), and cells producing gamma-retrovirus GALV-MLV (PG13-MFG-GFP line) (Fenard et al. 2013) were cultivated at 37° C., with 5% CO 2 in Dulbecco's modified Eagle's medium (DMEM+Glutamax) supplemented with 2 to 10% of fetal calf serum (FCS) inactivated by heat (Life Technologies, St-Aubin, France).
  • DMEM/FCS medium was buffered to the indicated pH values by using hydrochloric acid or sodium hydroxide, and was then sterilized on a filter (0.220.
  • the lentiviral vectors derived from HIV-1 were generated by transient transfection with calcium phosphate of 4 plasmids in HEK293T cells (Fenard et al. 2013): the expression plasmids of gagpol (pKLgagpol) and of rev (pBArev), the transfer plasmid coding for the green fluorescent protein GFP (pCCL-eGFP) and the plasmid coding for the GALVTR envelope glycoprotein (pBA.GALV/Ampho-Kana) or VSV-G (pMDG).
  • the HEK293T cells were washed and incubated in the DMEM/SVF medium buffered to the indicated pH value, comprised between 6 and 8. After 24 h of production, the viral supernatants were collected, filtered (0.450 and frozen at ⁇ 80° C. The titers of physical particles were determined by quantitative measurement of the p24 capsid of the HIV-1 by means of a commercial ELISA kit (PerkinElmer, Courtaboeuf, France).
  • the infectious titers were determined on HCT116 cells by detecting the GFP by flow cytometry (FACSCalibur, BD Biosciences, Le Pont de Claix, France), the titers being expressed in transduction units per milliliter (TU/ml) (Fenard et al. 2013).
  • Tubes for freezing of 1 ml containing GALVTR-LV supernatant (lentiviral vector pseudotyped with the envelope glycoprotein GALVTR) produced at pH 7.2 or 6 were incubated for the indicated time at 37° C. (the tubes with screw caps remaining closed). Next, the tubes were again frozen at ⁇ 80° C. and titrations on HCT116 cells were carried out simultaneously for all the conditions in order to prevent inter-experiment variations.
  • GALVTR-LV supernatant lentiviral vector pseudotyped with the envelope glycoprotein GALVTR
  • the first and second freezing/thawing cycles were carried out in parallel with two different samples from the same production of GALVTR-LV. This procedure allows the simultaneous evaluation of all the infectious titers of GALVTR-LV in order to avoid any inter-experiment variability.
  • the producing cells were washed and lyzed in a buffer containing 50 mM of Tris-HCl pH 7.5, 200 mM of NaCl, 1% of Triton X-100, 0.1% of SDS, 0.5% of sodium deoxycholate, 10% of glycerol, 1 mM of EDTA, and 1 mM of PMSF supplemented with a cocktail of protease inhibitors (complete protease inhibitor cocktail, Roche Diagnostics, Meylan, France).
  • the protein concentrations were determined by means of the Bio-Rad DC Protein Assay kit I (Bio-Rad, Marnes-la-Coquette, France).
  • the proteins (30 ⁇ g/track) were separated on 10% SDS-polyacrylamide electrophoresis gel (PAGE) and transferred on a nitrocellulose membrane Hybond ECL (GE Healthcare Life Sciences, Velizy-Villacoublay, France) and an immunoblot was produced by combining a goat anti-p24 antibody (AbD Serotec, Oxford, UK) and a mouse anti-actin antibody (AC-15 clone) (Sigma-Aldrich, St-Quentin-Fallavier, France). An anti-goat donkey antibody coupled with IRDye 800 and an anti-mouse donkey antibody coupled with IRDye 680 were used as secondary antibodies (Eurobio, Courtaboeuf, France). The immunoreactive bands were detected with the infrared Odyssey scanner and quantified with the analysis software Odyssey 3.0 (LI-COR Biosciences, Lincoln, Nebr.).
  • GALVTR-LV GALVTR envelope glycoprotein
  • FIG. 1 a The production efficiency of GALVTR-LV vectors in various culture mediums of pH 6 to 8 was evaluated ( FIG. 1 a ).
  • FIG. 1 b shows that the infectious titers obtained at pH 8 are strongly reduced relative to those at the typical pH of 7.2.
  • FIG. 3 shows that a medium at pH 6 allows significant increase in the production of infectious VSV-G-LV particles ( FIG. 2 a ) and of physical VSV-G-LV particles ( FIG. 2 b ), on average by a factor of 1.5, with stable specific activity ( FIG. 2 c ).
  • VSV-G-LV particles directly produced in a culture medium at pH 6 supplemented with FCS, are not only stable but also, unexpectedly produced at a higher level when they are produced from a culture medium at pH 7.2, conventionally recognized as optimal for this type of production.
  • the effect of the mildly acid pH was evaluated on the cell line PG13-MFG-GFP, producing GALV-MLV (MLV gamma-retrovirus pseudotyped with the envelope glycoprotein GALV) (Merten 2004).
  • the original PG13 cell line is a cell line of murine fibroblasts (NIH-3T3) transfected in a stable way with a packaging system of the MLV virus (pLGPS) and a construct coding for the GALV envelope glycoprotein (pMOV-GALV) (Miller et al. 1991).
  • the transfer plasmid coding for the GFP protein placed under control of the LTR promoter of MLV was introduced in a stable way into the PG13 line.
  • the PG13-MFG-GFP cells were incubated in DMEM buffered to pH 7.2 or pH 6 and 24 to 48 hours later, the contents of infectious particles in the harvested supernatants were evaluated.
  • FIG. 3 shows that the production of GALV-MLV particles is significantly increased at a mildly acid pH.
  • the harvested supernatants of lentiviral vectors are generally stored at ⁇ 80° C. before purification. It might have been assumed that the mildly acid pH conditions would have the deleterious effect of increasing the inactivation of the virions during the freezing or thawing procedure.
  • the supernatants of GALVTR-LV particles were therefore subjected to one or two freezing/thawing cycles, the infectious titers having been determined at each thawing step ( FIG. 4 a ).
  • FIG. 4 b shows that the mildly acid conditions do not affect the infectivity of the particles.
  • the average reduction in infectious titers after two freezing/thawing cycles as compared with a single cycle is only of 5% both at pH 7.2 and pH 6. The infectivity is therefore not altered when the lentiviral vectors are frozen under mildly acid conditions.
  • the target cells which in our case are mammal cells, are cultivated at a temperature of 37° C.
  • the tubes for freezing containing supernatant of GALVTR-LV vectors produced at pH 7.2 or pH 6 were incubated for 0 to 4 days at 37° C. and the infectivity decreased kinetics were tracked. As shown in FIG.
  • FIGS. 1 b and 1 d The amount of p24 proteins of HIV-1 harvested in the supernatants GALVTR-LV is improved under mildly acid conditions.
  • FIGS. 1 b and 1 d We therefore sought to determine whether this increase might be the consequence of an increase in the intracellular expression level of the p55gag precursor protein of HIV-1 in the producing cells.
  • FIG. 6 a an immunoblotting experiment shows an increase in the intracellular expression of p55gag at pH 6 relative to pH 7.2, with an average overexpression of 160% ( FIG. 6 b ).
  • This positive correlation between the intracellular overexpression of p55gag and the increase in the amounts of p24 protein in lentiviral supernatants suggests that mildly acid conditions generate an environment which is more favorable to optimal expression of the viral components.

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US12037599B2 (en) 2019-08-23 2024-07-16 Lonza Walkersville, Inc. Methods and constructs for production of lentiviral vector
US12365873B2 (en) 2021-01-28 2025-07-22 Allogene Therapeutics, Inc. Methods for transducing immune cells

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US12391960B2 (en) 2019-08-23 2025-08-19 Lonza Walkersville, Inc. Methods and constructs for production of lentiviral vector
US12365873B2 (en) 2021-01-28 2025-07-22 Allogene Therapeutics, Inc. Methods for transducing immune cells
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